With the recent rapid development of the information technology, a volume of information handled both in business world and private life has been increasing sharply. Also, a search technology to search desired information out of a huge volume of information more efficiently is deemed as an important factor in the information technology, and for this reason, corporations, institutions, etc. have been conducting a study of the search technology actively.
An information search apparatus, which has stored a huge volume of information in a database and conducts a search through the database with a search key to output a hit list (search result), has been used in various fields. Examples of the information search apparatus of this kind include: the one that presumes a cause (search result) from a symptom of machine trouble (search key), the one that presumes the name of a disease or a cure (search result) from symptoms (search key), etc. These information search apparatuses make highly intellectual judgments, and conduct fuzzy matching by using a database referred to as a knowledge database.
FIG. 16 is a view showing an example of an information search database 10 employed in a conventional information search apparatus. The information search database 10 is a type of the aforementioned knowledge database, and used in presuming a cause from a symptom of machine trouble. The information search database 10 is given with a definition of a cause-and-effect relation between “symptom” and “cause” related to the machine trouble.
More specifically, a plurality of concrete symptoms, such as “symptom 1”, “symptom 2”, “symptom 3”, . . . are described in the lateral direction, and “cause A”, “cause B”, and “cause C” corresponding to “symptom 1”, “symptom 2”, “symptom 3”, . . . are described in the longitudinal direction.
Precisely, the drawing shows that “symptom 1” (deficiency at high voltage), “symptom 2” (deficiency at low voltage), “symptom 3” (deficiency at high temperature), . . . in the first record are closely related to “cause A” (shortage of capacitor) in the cause-and-effect relation. Also, the drawing shows that “symptom 1” (deficiency at high voltage), “symptom 2” (deficiency at low voltage), “symptom 3” (deficiency at high temperature), . . . in the second record are closely related to “cause B” (memory cell leakage) in the cause-and-effect relation. Further, the drawing shows that “symptom 1” (deficiency at high voltage), “symptom 2” (deficiency at low voltage), “symptom 3” (noise at power source) . . . in the third record are closely related to “cause C” (cross talk) in the cause-and-effect relation.
With the conventional information search apparatus, if “deficiency at high voltage” and “noise at power source” are given as the symptoms, then the search result shows “cause C” alone as a probable cause. This indicates that a matching accuracy is high, in other words, the search result is narrowed. Hence, the searcher can take a prompt action for the machine trouble based on a single cause, “cause C”.
On the contrarily, if “deficiency at high voltage” and “deficiency at low voltage” are given as the symptoms, then the search result shows all of “cause A” through “cause C” as probable causes. This indicates the matching accuracy is low, in other words, the search result is not narrowed. Hence, the searcher has to take actions for the machine trouble based on all the three causes, “cause A” through “cause C”, and then narrow the three causes to one.
Incidentally, as has been discussed, with the conventional information search apparatus that conducts the fuzzy matching, when a single symptom corresponds to more than one cause for the structural reason of the information search database 10, more than one cause is outputted as the search result, which poses a problem that the matching accuracy is poor.
This problem becomes more apparent with an increasing volume of information stored in the information search database 10, and could result in a fatal problem that the apparatus can no longer function as a search apparatus when given with certain search criteria because of too many matching causes.